At MSK, research and development is given a lot of importance. There are dedicated qualified chemists, microbiologists and environmental scientists who are Doctorates and Post Graduates in their respective fields who devote themselves in this sphere. The research work is carried out in the R&D sections of the Central Laboratory for Minerals, Environment and Food. The objective of new method development is to meet highest standards of Accuracy and Consistency in test results. In other words, MSK is constantly working on framing newer methods that provide more precise and accurate results that are reproducible and repeatable. In addition to that MSK strives to reduce the turn around time of analysis in the laboratory by adopting newer techniques, wider use of instruments and by constantly challenging the status quo - the so called established method. Often customers demand alternate methods of testing, e.g one that can lower the detection limit of an element tested in a sample. Since all methods are not featured in International Standards such requirements cannot be readily met; MSK by virtue to its knowledge pool is however well suited to aid such a customer, often at no extra cost. Interestingly in this Technical Blog forum, MSK uploads all the new testing methods it develops successfully to share the findings with the wider world and to invite reviews.
An iron ore usually consists of hematite and other impurities like Alumina silicates. LOI for iron ores essentially corresponds to the combined water content from goethite / limonite and impurities such as Kaolinite etc, and to the CO2 content of carbonate phases. A study has been taken to find out the loss at different stages on heating from room temperature to 950oC in an inert atmosphere .The relationship between different losses at different temperature gave an idea about the presence of limonite, goethite, Kaolinite and Calcite also. So a broad idea about the basic nature of the ore was found out which is extremely useful for ore verification.
Three different iron ore sample with difference in iron percentage content were analyzed with help of TGA. An FTIR study was also taken to find out the presence of Fe-O-H bond. The main reactions occurring during heating of iron ores are:
• 100-150oC: Free water (moisture) removal
• 250-400oC: Release of combined water from hydroxyl iron minerals
• 400-600oC: Release of combined water from hydrated silico-aluminates
• 600-850oC: Loss of CO2 due to decomposition of calcite, magnesite, siderite
Besides these under oxidizing atmosphere, parasitic reactions can also occur (e.g. magnetite oxidizes to hematite).
A) Chemical Analysis of the Samples:
B) TGA & FTIR Analysis:
From TGA, presence of the iron Ore in difference phases specially limonite and goethite were studied and it was found that with decreasing concentration of iron in iron ore, concentration of goethite and limonite increases which is also evidenced from FTIR spectrum as shown below:
C) Comparison between TGA loss and wet analysis results:
Decomposition of goethite and limonite takes place at the same temperature zone. Scan accurate estimation of goethite and limonite are not possible. Limonite usually forms from the hydration of hematite and magnetite and all this study requires further confirmation by determination of C & H from CHN analyzer.
Contributed by: Ms. Alakta Saha under guidance of Prof. Barun Gupta
A silicone oil is any liquid polymerized siloxane with organic side chains. The most important member is polydimethylsiloxane. These polymers are of commercial interest because of their relatively high thermal stability and their lubricating properties.
Polymer backbone of silicone oil consists of alternating silicon oxygen atoms. According to the chemical structure, the silicone oil series can be divided into methyl silicone oil, ethyl silicone oil, phenyl silicone oil, methyl hydrogen-containing silicone oil, methylphenyl silicone oil, methyl chlorophenyl silicone oil, methyl ethoxy silicone oil, methyl propyl silicone oil, methyl vinyl silicone oil, methyl hydroxyl silicone oil, ethyl hydrogen-containing silicone oil, hydroxyl hydrogen-containing silicone oil, cyanogen-containing silicone oil and so on. Silicone oil can be prepared by dimethyl cyclosiloxanes and hexamethyldisiloxane conducted telomerization under the presence of catalysts. Its viscosity was increased by the number of silicone chain sections in the molecule, from the easily flowing liquid to a thick semi-solid. It is generally colourless or pale yellow, odourless, non-toxic, non-volatile liquid. It has excellent heat resistance power, electrical insulation, weather resistance, hydrophobicity, physiologically inert & smaller surface tension.
Silicone oil is used as a long-term release agent in the contour machining of plastic and rubber as well as in food production. It is also used as high and low temperature lubricant between various materials, manufacturing the additives of lubricating plastics. glass, ceramics, metal, cement and other products which when treated with dimethylsilicone oil are not only hydrophobic, but also corrosion resistance, mildew proof, surface smooth. It is widely used as heat carrier and efficient defoamers in the chemical, pharmaceutical, cosmetics materials, food and other sectors, quakeproof damping material in precision machinery and instrumentation, high-temperature resistance dielectric liquid in the electric appliance and electronics industry. It also widely used as polishing agent of automotive, furniture, floor, as well as hydraulic oil of pumps, brakes , cylinders and so on.
Experimental & Results:
Silicon & other trace elements were quantatively estimated by Perkin Elmer optima 7000 DV ICP-OES. Thermogravimetry analysis was done using Perkin Elmer STA 6000 TG/DSC instrument. The samples were also studied by Thermo Scientific Nicolet IS10 Fourier Transmission Infra-red Spectrometry.Viscosity of the samples were measured using Red Wood Viscometer.
a) ICP-OES Analysis: The samples were acid digested using acid digestion vessel.Calibration curves were made using reagent blank & analysed standard of pure standard liquid CRM of required strength. The following figures show the calibration curves made for analyzing different element in ICP and their spectrum details. The table shows silicon and trace element concentration analysed in ICP for five different grades of silicone oil samples received at laboratory.
b) TG/DSC Analysis: Analysis was performed at a heating rate of 10°C /min in pure nitrogen gas atmosphere upto 350°C & after that in zero air upto 700°C. From TG/DSC curves, it was observed that there was loss which took place upto 350°C (approximately).Volatile matters were volatilized at this temperature. Again loss was observed within 350°C to 700°C. It indicates the presence of different volatile matters which decompose at different temperature zone.
c) FTIR Analysis: The samples were dissolved in pure xylene. 10% sample solutions were prepared & scanned was carried out from the region of 4000 cm-1 to 400 cm-1. The region was zoomed form 3000 cm-1 to 1000 cm-1. Same treatment was done using 5% i.e diluted sample solution. The following figures show the FTIR spectrum of each of the 5% silicone oil solution.
It was observed from the FTIR scan of all the five silicone oil samples that Aliphatic –CH3 asymmetric stretching (2975-2950 cm-1), stretching frequency of carbon carbon triple bond are absent. Stretching of Isopropyl group (1390-1380 cm-1), C=C stretching (2000-1540 cm-1), -SiH3 symmetric stretching (2153-2142 cm-1) , Si-C stretching (1280-1255 cm-1) are present.Small quantity of Si-O-Si (1130-1000 cm-1) & Si-O-C stretching (1110-1000 cm-1) are also present.
d) Viscosity Measurement: Viscosity of four Silicone Oil (except Silicone Oil 5 as it is semi-solid) was measured at 40°C.
It was found from FTIR study that few hydrocarbon groups are present. TG/DSC study indicates that those volatile hydrocarbons are volatilized into two steps, one is at approximately 350°C & other 350°C – 700°C. It can be concluded that those silicon oils which show more loss contain more hydrocarbons.
Contributed by: Ms. Priya Das, Mr. Raju Bera and Mr. Monojit Roy under the guidance of Prof. Barun Gupta.
An Investigation On Transportable Moisture Limit (TML) Of Coal Using Proctorfagerberg Method
Coal is an organic material which has been subjected to heat and pressure over time. It is primarily composed of carbon with variable quantities of other components and it changes in the proportions of carbon to the other components which describe the coal rank. As the rank increases, which is as a result of the effects of increasing pressure and temperature over millions of years, so too does the calorific value. Coal is usually shipped in the form of lumps, but some are very fine grained (called ‘fines’) and may exhibit liquefaction characteristics, hence these require further loading controls in the form of a Transportable Moisture Limit Certificate (TML) and a Moisture Content (MC) Certificate. The International Maritime Organization (IMO) has put guidelines in place on how shippers can monitor their moisture control methods, and the Competent Authority of the Port of Loading is now required to supply an additional certificate which details their approval of these methods. Another coal-related cargo is listed as Coal Slurry, and this also consists of fine coal particles, often washed off larger lumps. Since this too can liquefy, it requires a TML Certificate and MC certificate prior to loading. After the mandatory implementation of the International Maritime Solid Bulk Cargoes Code (IMSBC Code) from 1stJanuary 2011 along with the recent incidents involving bulk carriers have encouraged research institutions and industry partners to perform extensive studies into the test methods used to determine the Transportable Moisture Limit (TML) of ‘Group A’ or liquefiable cargoes.
In the present work, an effort has been made to determine the TML values of different types of coal. The modified Proctor Fagerberg method has been adopted to determine this property. The test method is based upon use of the Proctor apparatus developed in soil mechanics. The standard Proctor/Fagerberg test was adopted by the International Maritime Organization, for use in the IMSBC Code, between 1991 and 1998 for ores. However, in order to have a concrete understanding about the process further research work has been carried out and this work still continues.
In general, TML is the moisture content corresponding to the intersection of the 70%degree saturation curve and the test sample compaction curve. In the case of coal sample where moisture freely drains from the sample such that the test sample compaction curve does not extend to or beyond 70% saturation, the test is taken to indicate a cargo where water passes through the spaces between particles and there is no increase in pore water pressure. Therefore, the cargo is not liable to liquefy. The following definitions are helpful to interpret the results of the TML determination of coal:
Degree of Saturation: Percentage of voids of the test portion occupied by water.
Gross Moisture Content: The mass of moisture divided by the wet mass of the sample.
Optimum Moisture Content: The moisture content corresponding to the maximum compaction under the specified compaction condition.
True Density: Mass in air of a unit volume of particles of coal excluding the volume of the voids between and within the particles.
Transportable Moisture Limit: Maximum moisture content allowed for a safe maritime transportation of a cargo of material. For coal, the TML is the moisture content at 70% degree of saturation.
At least 20 kg was obtained for this test for a particular specimen. To minimize changes to the flow characteristics of the sample, it shall not be completely dried during its preparation. The sample selected for this study was below -6 mm size and the moisture of the sample reduced to 4-6%. The test sample was homogenized thoroughly and split it into 10 test portions of approximately 1.5kg each. Each test portion was stored in a closed recipient to avoid any extra moisture intake from the atmosphere. The material preparation and testing procedure was accomplished within a reasonable time to minimize moisture losses. All suitable sample containers, including plastic sample bags used for the test were carefully sealed.
1. Proctor/Fagerberg Mould: A cylindrical iron mould, having capacity of 1000 cm3 with an internal diameter of 105mm ± 0.5mm and height 115.5mm ± 1mm or with an internal diameter of 100mm ±0.4mm and height of 127.3mm ± 0.3mm. The mould is fitted at its upper end with a removable extension collar of the same internal diameter and having approximately 50mm height
2. Proctor/Fagerberg hammers: Metal made having 50mm diameter and weighing 350g equipped with a pipe open at its lower end and a suitable arrangement for controlling the hammer drop height to 200 mm
3. Drying Oven: Equipped with a temperature indicator and control apparatus of regulating the temperature at any point in the oven at 105°C ± 5°C and so designed as to maintain the temperature
4. Pycnometer: Preferably water or kerosene oil pycnometry equipment to determine the density of solid material
5. Tray for hand mixing
6. Weighing device
7. Spray bottle
1.5kg in each set of test portion was taken and known amount of water was added into it. The mixture was packed very tightly in airtight condition .After 24hr of saturation, the sample was equally divided into 5 parts. One of these parts was placed into the mould, levelled and then tamped uniformly over its surface by dropping the hammer 25 times vertically through the full height of the guide pipe, moving the guide pipe to a new position after each drop. The procedure was repeated four more times so that there are 5 tamped layer of materials in the mould. The following picture shows coal sample compacted within the mold:
After the last layer has been tamped, the extension portion of mould was removed without disturbing the compacted sample inside. The top of the compact sample was leveled off in the mould using a straight edge. The mass of the mould with the compacted ore was initially determined .Thus the mass of the wet sample was calculated. The test portion was removed from mould, speeded it on a tray and placed it in an oven at 105°C until constant mass was achieved. The mass of dried sample was determined in this way. The procedure was repeated for the other test portions prepared with different moisture content on the compaction curve. For each compaction test, a predetermined amount of water was added to the test portion in a plastic bag. The water content was chosen so that at least one point is above the Optimum Moisture Content (OMC) to define the compaction curve appropriately.
Results & Interpretation
Variables and definitions:
The variables and definitions used in the determination of TML are as follows:
A = empty mould mass in grams.
B = mass of mould with tamped test portion in grams.
C = wet mass of test portion in the mould in grams = B – A.
D = dry mass of test portion removed from the mould in grams (used for moisture determination).
E =mass of water in the mould.
W1=gross water content.
d= true density of solid material.
V =Volume of mould.
ρw= density of water.
Calculation & Expression of key parameters:
P: Dry bulk density (g/cm3)
ev : Net Water content (percentage by volume)
ev= (E/D) ×( d/ρw) ×100 where, ρw= density of water
e: void ratio (volume of voids divided by volume of solids)
e = (d/P) – 1
S = degree of saturation (percentage by volume)
S= ev/ e
W1 = gross water content (% by mass)
W1= (E/C) × 100
W = net water content (% by mass)
W = (E/D) × 100
TML = 100 × ev / [(100 × d) + ev]
Experimental Data & Compaction Curve for Coal #1:
Experimental Data & Compaction Curve for Coal #2:
The critical moisture content is determined from the intersection of the compaction curve and the line S = 70% degree of saturation. The gross water content corresponding to this intersection is known as the Transportable Moisture Limit (TML). The Optimum Content (OMC) is the gross moisture content corresponding to the maximum compaction (maximum dry density and minimum e) under the specified compaction condition.
TML is a significant issue for very fine products where there is danger of liquefaction of the products in the holds of the ship, thus leading to cargo shifting and progressive listing of the vessel. However, this property has generally not been an issue of coal transport other than the occasional cargo of reclaimed wash plant fines or some small shipments of very fine grind washed metallurgical coals. The Proctor Fagerberg Method has been successfully used during the present work to determine TML of different grades of coal viz., both low and high moisture holding capacities. In future this method could be adopted for other solid fuel cargoes required to be transported safely to their destination point.
Contributed by: Sabir Laskar, Sourav Bharati and Dolagobinda Sahoo
Complexometric Determination of Copper & Its Comparison Against Iodometric & Electrogravimetric Estimation
Copper occurs both in combined state and free state and also in many ores. The abundance of copper in earth’s crust is estimated to be 70 parts per million. The important ores of copper are: Copper pyrites or Chalcopyrite (CuFeS2), Cuprite (Cu2O) and Copper glance (Cu2S). The leading producers of copper are Chile and the United States. Nearly half of the world’s copper comes from these two countries. The next largest producers are Canada, Peru, Australia, Russia and Indonesia. About 98% of copper mined in the United States comes from Arizona, Utah, New Mexico and Nevada. In India the major copper mines are Khetri copper belt in Rajasthan, Singbhum copper belt in Bihar and Malanjkhand copper belt in Madhya Pradesh. Mining production is just 0.2% of world production. There have been various ways for volumetric determination of copper such iodometric, complexometric, elecrogravimetric, potetiometric etc among which iodometric method is the commonly adopted standard method prescribed under ISO 10258:2015. During iodometric estimation of copper two important sources of error may occur: a) loss of iodine owing to its appreciable volatility and acid solution of iodine are oxidised by oxygen from the air by the equation as shown below:
The stability of thiosulphate solution is also to be taken into consideration. Ordinary distil water usually contains an excess of carbon-di-oxide; this may cause slow decomposition to take place with the formation of sulphur as below:
Moreover, decomposition may also be caused by bacterial action (eg., thiobacilus thioparus) if the solution has been standing for some time. Exposure to light also may accelerate the decomposition of thiosulphate solution. On the other hand, the complexometric estimation of copper with EDTA using murexide as indicator is a simple, rapid and accurate method.
Copper (II) can be determined quantitatively by complexometric direct titration with EDTA in slightly ammoniacal solution (pH 8-9). Murexide serves as the complexometric indicator which is purple when it is free (H4In_) and yellow when complexed with copper (II).
The complex dianion has the structure shown below. Note that the anion completely surrounds the cation, forming six co-ordinate cation bonds to copper and a very stable complex. The bonding to the copper ion is nearly octahedral.
It should be noted that this method is only applicable to solutions containing not more than 25 mg copper ions per 100 ml of solution; if the concentration of Cu(II) ion is too high, the intense blue colour of the copper(II) amine complex masks the colour change at the end point. Please note that during titration, freshly prepared indicator solution to be used. The copper indicator complex is purely yellow, but at the starting point of titration the colour may be slight greenish depending upon the amount of copper present.
0.5 gm concentrate was weighed into a 500 ml beaker. 20 ml of mixed concentrated hydrochloric, sulfuric and nitric acids (1:1:1) was added and gently heated until the digestion was complete.5 ml of concentrated sulfuric acid was added and the heating was continued till sulfur trioxide fumes were evolved. The contents were cooled to room temperature.100 – 150 ml water was added and the solution was gently heated till all the salts formed were dissolved. The solution was filtered and the residue was washed with 5 ml sulfuric acid and subsequently with hot water. The filtrate and the washings were collected into a 400 ml beaker. Copper was separated by double mixed oxide precipitation with ammonium chloride- ammonium hydroxide. The blue colored solution was taken in 500ml beaker and acidified with 1:1 HNO3, boiled gently for a few minutes in order to expel oxides of nitrogen, cooled and finally taken into 500 ml volumetric flask. 10-20 ml of aliquot (depending upon the concentration of copper) was taken into 250 ml conical flask, added 1:1 ammonia solution until the light blue precipitate first formed just dissolves to form clear blue solution, diluted to 100 ml with distilled water, same quantity of murexide indicator added and titrated with 0.01M EDTA until colour changes from yellow to deep purple.
The entire analysis was carried out using a copper concentrate material for which copper estimation was carried out using complexometric, electrogravimetric and iodometric method for comparison of results. During complexometric method, all experiments were carried out using same quantity of sample solution and same amount of indicator. The findings obtained by complexometric method have been well supported by electro-gravimetric and iodometric estimation. The following table illustrates the results below:
Estimation of copper by complexometric method is a fast, accurate and less time consuming method. It is a technique with less stringent requirement of maintaining the environmental condition as compared to iodometric estimation of copper. The reagents used are also less expensive. Moreover, the repeatability of the method is quite good with low standard deviation. Consequently this method is very much applicable to determine copper.
Contributed by: Kajal Ray under the guidance of Prof. Barun Gupta